Continuous ink-jet recording

ABSTRACT

The ink-jet recording system comprises a rotor on whose cylindrical surface rests a recording support, and a annular inkjet nozzle system which is stationary in relation to the rotor. At least one supply roll and one take-up roll for the sheet-form recording support are arranged on the rotor. These rolls are connected to the rotor so that the recording support makes both a rotary and a translatory movement in operation relative to the stationary nozzle system. In a preferred embodiment the rotor in the form of a solid cylinder and the recording support is guided externally over the surface of the rotor. In this embodiment, the stationary annular nozzle system is arranged over the surface of the rotor.

United States Patent [191 Wick et al. Au 6 1974 [54] CONTINUOUS INK-JETRECORDING 3,416,153 12/1968 Hertz et al. 346/75 [75] Inventors: RichardWick, Munich; Rudolf Meyer; Klaus Hoffmann, both of PrimaryExaminer-Joseph W. l-lartary Leverkusen, all of Germany Attorney, Agent,or Firm-Connolly and Hutz [73] Assignee: Agfa-GevaertAktiengesellschaft,

Leverkusen, Germany [57] ABSTRACT [22] Filed: Sept. 18, 1973 I Y Theinket recordlng system comprises a rotor on PP whose cylindrical surfacerests a recording support, 1 and a annular ink-jet nozzle system whichis stationary [30] Foreign Application Priority Data in relation to therotor. At least one supply roll and t 23 1972 Gama 2246797 one take-uproll for the sheet-form recording support ep are arranged on the rotor.These rolls are connected I to the rotor so that the recording supportmakes both [52] 178/66 a rotary anda translatory movement in operationrelative to the stationary nozzle system. In a preferred eml' Gold 1 216 bodiment the rotor in the form of a solid cylinder and 6 the recordingsupport is guided externally over the surface of the rotor. In thisembodiment, the station- 56] References Cited ary annular nozzle systemis arranged over the surface of the rotor.

UNITED STATES PATENTS 3,130,931 *4/1964 Hautly 346/l38 UX 20 Claims, 14Drawing Figures Pmmmms 61974 saw an or 1o PAHNIEDMB 14 Y 3.8%.355

sum :05 or 10 PAIENTEU MIC 74 saw as or 1o PATENTEU AUG 6 I974 sum 07 or10 FIG. 70

PAIENIEDAUB 6:914

saw '08 or 10;

Axsmwwe 61914 3.828.355

' sum "09 or 1o FIG. 72

ummus SIHH 3.828.355

sum '10 or 10 CONTINUOUS INK-JET RECORDING This invention relates to anapparatus for continuously recording ink-jet pictures. It comprises arotor on whose cylindrical surface rests a recording support, and anannular ink-jet system.

In ink-jet recording, ink or coloured liquid is extruded under highpressure through a nozzle (capillary), Immediately downstream of thenoule is an annular control electrode. A voltage U is applied betweenthis electrode and the'conductive ink or coloured liquid. When U exceedsa certain limit (about 200 volts), the jet of ink breaks up into smalldroplets. The higher the voltage U, the greater is the degree ofdisintegration.

The unbroken jet passescompletely through a small diaphragm aperture-andstrikes the support guided past the diaphragm'However, the dropletsdiverted from the linear path drop onto the diaphragm and are filteredoff under suction through a sintered metal filter. The higher thevoltage U, the smaller the quantity of ink or coloured liquidwhich'reaches the support. The principle of this process is described indetail in German Auslegeschrift 1,271,754.

One serious disadvantage attending most conventional ink-jet recordingprocesses is that they are not continuous (US. Pat. No. 3,404,221). Therecording material in the form of paper or film is stretched in the formof a single sheet across a rotating roller and has to be removed oncompletion of a picture whose size is limited by the size of the drumcasing.

In order to obtain continuous picture recording, it has now beenproposed to fit a number of nozzles togetherin a row to form a nozzlecomb and to arrange several such nozzle combs one behind the other in astaggered pattern so that the openings of all the nozzles lie in oneplane. A sheet guided past in this plane is then uniformly covered withparallel rows of drops (cf. for example DOS 1,941,680). In thisarrangement, therefore, each picture line is recorded by a differentnozzle. This calls for an extremely large number of nozzles forproducing high-resolution pictures and since each nozzle together withits control unit takes up a certain amount of space, it is alsonecessaryto have a number of nozzle rows which have to be adjusted in relation toone another.

It has also been proposed to record continuously on supporting sheets byguiding the droplet generators arcuately over the recording support inthe scanning direction, rather than arranging them fixedly or advancingthem slowly at right angles to the scanning direction, in which case thesheetform recording material makes a slow translation movement (DOS1,936,518), or by mounting the droplet generators inside a semicylinderfor rotation about the axis of this cylinder and having them spray ontothe recording support which is advanced on the inside of the cylinder inthe axial direction.

Unfortunately, all arrangements in which the droplet generators aremoved quickly in the scanning direction are attended by the disadvantagethat electrical signals, high pressures and coloured liquids have to betransmitted to components rotating at high speed. In many cases, thismeans that picture quality is adversely af fected.

An object of the invention is to provide an apparatus for the continuousrecording of ink-jet pictures which gives high picture quality and isrelatively simple and compact in structure. It is armed to do this withas few ink nozzles as, possible so that only a correspondingly smallnumber of transmission channels need be used. A small number oftransmission channels means less Outlay in terms of electronics ans alsofar less troubleprone operation.

According to invention, here is provided an apparatus for continuouslyrecording ink-jet pictures comprising a rotor having a cylindricalsurface, and an annular ink-jet nozzle system, wherein the ink-jetnozzle system is stationary in relation to the rotor, and at least onesupply roll and one take-up roll are arranged on the rotor for at leastone recording support in guided sheet form each of which is guided overthe rotor surface being connected to and rotating with the rotor so thatthe or each recording support simultaneously makes a rotary andtranslatory movement in relation to the stationary nozzle system.

In one embodiment of the invention, the rotor is in the form of a hollowcylinder and the recording support is guided over the inner surface ofthis hollow cylinder. In this embodiment of the invention, thestationary, annular nozzle system is arranged inside the hollowcylinder. In another preferred embodiment of the invention, the rotor isin the form of a solid cylinder and the recording support is guidedexternally over the surface of the rotor. In this case, the stationaryannular nozzle system isarranged over the external rotor surface.

The sheet-form recording material is guided'over the rotor surfaceeither helically or parallel to the rotor axis. I Guide rollers areadvantageously arranged in the vicinity of the supply rolls'andtake-uprolls to guide the sheet from the supply rolls onto the rotorsurface and from the rotor surface to the take-up rolls.

In one preferred embodiment, the supply roll and take-up roll arearranged inside the rotor and their axes are inclined towards the rotoraxis in accordance with the directions in which the sheet runs onto andoff from the rotor surface. The supply roll and take-up roll arepreferablyarranged on the rotor axis. In this case, the

axes of the guide rollers have to be inclined relative to the rotor axisin such a way that the recording sheet is turned through 90 into a planetangential to the rotor surface. The angle of inclination a of the guiderollers with respect to the rotor axis is advantageously selected tocorrespond to the relation a yU where a is the angle at which the sheetruns onto and off from the rotor surface, whilst U is the degree oflooping around the guide roller. In a further improvement, the degree oflooping around the guide rollers is kept constant. For this purpose,additional guide rollers are arranged in the vicinity of the supply andtake-up rolls.

The rate of sheet advance is determined by the guide rollers. For thispurpose, at least one of the guide rollers is driven.

The drive system is preferably such that the ratio of the peripheralspeed V of the rotor to the rate of sheet advance V is constant.

In the embodiment in which the recording sheet is guided parallel to therotor axis, the supply rolls and take-up rolls are advantageouslydistributed uniformly around periphery of the rotor at both endsthereof. The supply rolls and take-up rolls are arranged opposite oneanother.

In another embodiment, the supply rolls are arranged at one end and thetake-up rolls at the other end of the rotor adjacent one another on therotor axis. In this way, imbalance of the rotor is minimised from theoutset.

According to another aspect of the invention, contact rollers areprovided on the rotor surface, bringing the recording sheet into contactwith the rotor surface in the vicinity of the nozzle system. In analternative embodiment, the recording sheet is drawn onto the rotorsurface by means of a-vacuum. For this purpose, the rotor surface isprovided with bores'and the inner v compartment of the rotor connectedto a vacuum pump.

In cases where the recording sheets are guided parallel-to the rotoraxis, it is of advantage to bevel the rotor surface frusto-conicallytowards its ends. The flat recording sheets are thengradually convertedinto the curved form. In this-embodiment as well, the guide rollersarepreferably inclined to the rotor axis in such a way that therecording sheets are always through 90 into .a plane tangentialto'therotor surface." As in the helical sheetguide system, additional guiderollers are again arranged in the vicinity of the supply rolls andtake-up rolls to ensure that the looping angle around the guide rollsremains constant. I

'The recording sheets should slide over the rotor surfacewith minimalfrictional resistance. In this respect, it is'proved to be of advantagefor the rotor surface to consist of a hydrophobic material.

An advantage of the invention is that a large number sociated controlsystems. The recording support is in the form of paper sheeting 8 whichis guided helically over the rotor surface 5 by means of guide ridges 9.The

supply roll and the take-up roll for the recording paper are situatedinside the rotor 2. Guide rollers 10a and.

10b are provided on the rotor surface 5 which make it easier for thepaper 8 to run onto and off from the rotor surface 5. Accordingly, thepaper 8 slides helically over the rotor surface 5 and passes throughbeneath the stationary nozzle system 6. In order to reduce friction, therotor surface is coated with a hydrophobic material.

of ink-jet pictures can be continuously recorded without any need forcomplicated manipulation of the recording apparatus. The recordingsupport does not have to be continually refitted as before. Control ofthe nozzle system involves relatively little outlay in terms ofelectronics and the probability of faults occurring through theelectronics is thus reduced.

Embodiments of the invention are described by way of example. below withreference to the accompanying drawings, wherein:

FIG. 1 illustratesthe principle of ink-jet recording (prior art). Y

FIG. 2 is a diagrammatic perspective view illustrating the recordingapparatus according to the invention.

FIG. 3 illustrates an embodiment in which the recording support isguided over the inner surface of a hollow rotor.

FIG. 4 shows a rotor of the kind illustrated in FIG. 2, in which therecording sheet is guided helically over the outer surface.

FIG. 5 is a side elevation of the rotor shown in FIG.

FIGS. 6 to 8 show how the sheet is guided from a supply roll to therotor surface by means of obliquely arranged guide rollers.

FIG. 9 shows the extent to which recording is governed by angle in thecase of helical guiding.

FIG. 10 shows an embodiment in which the recording sheet is guidedparallel to the rotor axis.

paper 8 makes a rotary and translatory movement in relation to thestationary nozzle system 6. In this way,

each point of the recording paper describes a helical linein relation toa stationary nozzle 7 aslong as it is situated on the rotor surface. '1

FIG. 3 shows an embodiment in which the rotor 2 is in the form of ahollow cylinder. In this case, the nozzle system 6 is installed insidethe rotor 2. The nozzles are connected to a supply through ink lines 6a.The recording sheet 8 is guided over the" concave inner surface of therotor 2. The rotor casing is provided with bores 11 which open intovacuum chambers 12. The'recording sheet 8 is drawn onto the rotorsurface under the effect of the vacuum and is in complete surfacecontact with it; 1 i Some difficulties are involved in guiding therecording sheet from the supply roll to the take-up roll. This operationis described below with reference to FIG. 4.

. As in FIG. 2, the recording sheet 8 is guided helically FIG. 11 showsthe arrival of the recording sheet on over the outer surface 5 of therotor. The sheet 8"is guided from a supply roll 13 situated inside therotor 2 overthe guide rollers l0aand 10b onto the rotor sur'-' face 5.At the other end ofthe rotor 2, it is guided over similar guide rollersto a take-up roll 14. The take-up roll 14 is driven by an electric motorthrough a friction clutch. However, the sheet is actually advanced bythe guide rollers 10b in the vicinity of the take-up roll 14. In orderto ensure that the sheet is always in firm contact with the rotorsurface and does not flap, the

guide rollers 10a and the supply roll 13 are provided with a frictionbrake. In addition, the friction brake on the supply roll 13 ensuresthat it is only the required length of sheeting which is run-off. Theaxes of the supply 'roll 13 and take-up roll 14 are inclined towards therotor axis 15 in accordance with the directions in which the sheet runsonto and off from the rotor surface. This inclined arrangement preventsthe recording sheet 8 from shooting out sideways.

FIG. 5 is a side elevation of the arrangement illustrated in FIG. 4. Therecording sheet 8 runs onto the rotor surface 5 from the supply roll 13over the guide rollers 10a. There is a recess in the rotor surface inthe vicinity of the guide rollers 10a. The outside of the nozzle system6 is arranged concentrically around the rotor 2.

One particularly advantageous embodiment uses an oblique guide roller 16(FIGS. 6 to 8). In this arrangement, the supply roll 13 is arranged onthe rotor axis 15 and not inclined thereto. The recording sheet 8 isdirected into a helical path on the rotor surface by the guide roller 16whose axis is directed obliquely of the rotor axis 15 and henceobliquely of the axis of the supply roll. The angle of inclination 'y,at which the recording sheet 8 moves into its helical path, is governedboth by the angle a of the axis of the guide roller 16 with respect tothe rotor axis and by the looping angle g of the recording sheet 8around the guide roller 16. The values of -y, a and g are related by theequation a 'y-g. If, for example, the looping angle g is one-half, theangle a between the guide roller 16 and rotor axis 15 is half as largeas the angle y at which the recording sheet 8 moves into its helicalpath. Since as operation continues the diameter of the supply roll 13becomes progressively smaller, the looping angle g and hence thehelical-path angle 7 would alter continuously in the absence of anyadditional measures. For this reason, additional guide rollers 17 areprovided to ensure that the looping angle g remains constant. Similarly,guide rollers 16 and 17 are also arranged in the vicinity of the take-uproll at the other end of the rotor. One of the guide rollers 16 is againresponsible for sheet advance.

FIGS." 2m 5 show the nozzle system fixedly arranged in a circle aroundthe rotor 2 in the middle between the offwinding guide rollers a and theonwinding guide rollers 10b. The number of loops of the recording sheet8 around the rotor 2 between entry and contact determines the size ofthe area available for the ink nozzles 7. For one complete loop, thisarea is equal to zero. In the case of a double loop, and if it isassumed that the sheets 8 lie close together, the area F available forthe ink nozzles 7 is given by:

F=B Z B where B is the width of the recording support and d the diameterof the rotor 2. More generally, when the looping angle U is included,

Since, in the method of picture recording described here, the picturetrace of an ink nozzle 7 appears as a spiral line on the stretchedrecording support due to the rotation and simultaneous translation ofthe recording sheet, it is important to know the extent of the interval,more particularly the vertical interval, between two picture tracesbecause this interval determines the number of ink nozzles 7 which haveto be used to fill the gap between these ink traces with further inktraces.

FIG. 9 illustrates parameters governing this which are explained in thefollowing, and the flattened recording sheet of one loop in its correctposition to the rotor axis with the ink traces produced on the basis ofthe V speed of the recording support relative to the rotor V resultingspeed of the recording support when V and V have substantially the samedirection. The angle at which this speed is reached is desig- VI rEsuIti ngspeed of the recording support when V and V are substantiallyoppositely directed. The corresponding angle is designated B If theconditions are calculated with the parameters defined abovggz cording toFIG. 9, then:

B 1/-= V a a vl dn V1 111 The conditions are illustrated by thefollowing numerical example. Suppose that d cm B 10 cm V 500 cm/sec V 50cm/sec.

The following intervals are then obtained for b and If it is desired tofill this gap with inknozzles in a den sity of 10 nozzles/mm, it isnecessarythat z 91 and z l l l ink nozzles. If it is calculated thateach ink nozzle with its associated control system occupies about 1 cmthe looping angle U can be approximately determined as being U =1.l; Ul.15.

In cases where it is desired to apply multicolour information, thenumber of ink nozzles is increased accordingly, as is the spacerequirement and looping angle.

It is possible with a predetermined number of nozzles, z,recording-support width B and rotor diameter d, to determine the ratioof the speeds V /V It is of the utmost importance to'maintain the ratioV /V in operation in order to ensure-the precise connection of two scanzones after one revolution of the rotor. For this reason, a regulatingmechanism (not shown) is incorporated in the arrangement, beingresponsible not only forthe constancy of revolution but also for theconstancy of V /V Since an asymmetrical distribution of mass about therotor axis is present in the rotating system with all its fittings, thesystem has to be balanced by applying additional masses to it beforeoperation in order to minimise the forces acting on the bearings. It iseven of advantage, in the interests of highly desirable synchronismwhich promotes picture quality, to arrange additional flywheel masses inorder to correct minor fluctuations in regulation.

The arrangement described above is distinguished by the fact that, inaddition to the rotation of the rotor 2, the recording sheet makes ahelical movement onthe rotor surface 5. Accordingly, the recording sheet8 spontaneously makes both a rotary and also a translatory movement.

An alternative embodiment which has also proved to be effective is shownin FIG. 10. In this case, the recording sheet 8 only makes a translatorymovement. The rotary movement relative to the stationary nozzle system 6is made solely by the rotor 2. In this case, the supply rolls 13 andtake-up rolls 14 are arranged opposite one another at the ends of therotor 2. The recording sheet 8 runs over the rotor surface parallel tothe rotor axis 15. Since the recording sheet 8 is fairly thin and is notvery stiff against flexure according to its inner consistency, it isreadily possible by maintaining a certain minimum interval between thesupply rolls 13 and take-up rolls 14, to deform the sheet in such a waythat it applies itself uniformly to the cylindrical rotor surface. Inaddition, pairs of contact rollers 18 ensure that the recording sheets 8are uniformly applied to the rotor surface in the vicinity of theannular, stationary nozzle system 6.

The entire system, including the supply rolls l3 and take-up rolls 14,rotates about the rotor axis 15. At the same time, the recording sheets8 follow a translatory path, i.e. from the supply rolls 13 to thetake-up rolls 14 in the direction of the rotor axis 15. The annularnozzle system is arranged substantially in the middle of the-rotor 2.The interval b between two ink traces after one revolution is given bythe relation where V sheet speed in the direction of the rotor axis V,tangential speed of the rotor at the rotor surface,

B width of the recording sheet.

The transition of the recording sheet 8 from the flat form at the supplyrolls 13 into the curved form onthe rotor surface 5 is facilitated by aspecial configuration of the rotor 2 at its ends'(cf. FIGS. 11 and 12).The delivery rolls 19 guide the flat sheet from the supply rolls 13towards the rotor 2. The beginning of the rotor 2 is frusto-conical sothat the flat recording sheet 8 is gradually converted into an arcuateform. The frustoconical portion stops in the vicinity of the nozzlesystem 6 where the recording tape 8 follows the rotor surfaceparticularly closely under the effect of the contact rollers 18. FIG. 12is a sideelevation of FIG. 11. The gradual transition of the recordingsheet from its flat form into its arcuate form can be seen particularlyclearly in FIG. 12. Instead of providing contact rollers 18, the rotorcan alternatively be in the form of a suction roller. In this case, therecording sheet 8 is drawn onto the rotor surface by vacuum.

The arrangement of the supply rolls 13 and take-up rolls 14 is by nomeans confined to the embodiment shown in FIG. 10. It can be used in thesame way as in the case of the hollow cylinder rotor shown in FIG. 3.

In the arrangment shown in FIG. 10, where the supply rolls l3 andtake-up rolls 14 are distributed uniformly over the periphery of therotor 2, there is a relatively high moment of inertia. For this reasonthe rotor bearing has to be made correspondingly strong. Much morefavourable in this respect is an embodiment in which the supply rolls 13are arranged at one end and the take-up rolls 14 at the other end of therotor 2 alongside one another on the rotor axis 15. In this case, as inthe embodiment shown in FIGS. 6 to 8, the recording sheet 8 is turnedthrough 90 into a tangential plane to the rotor surface by oblique guiderollers 16 and additional guide rollers 17. This embodiment is shown inFIGS. 13 and 14. As already described, the direction followed by therecording sheet 8 after it has left the guide roller 17 is determined byits inclination in relation to the rotor axis 15 and its looping angleby the recording sheet 8. FIGS. 13 and 14 again show the frusto-conicalincline of the rotor and the gradual transformation of the recordingsheet into an arcuate form.

What we claim is:

1. An apparatus for continuously recording ink-jet pictures comprising arotor having a cylindrical surface, and an annular ink-jet nozzlesystem, wherein the ink-jet nozzle system is stationary in relation tothe rotor, and at least one supply roll and one take-up roll arearranged on the rotor for at least one recording support in guided sheetform each of which is guided over the rotor surface being connected toand rotating with the rotor so that each recording supportsimultaneously makes a rotary and translatory movement in relation tothe stationary nozzle system.

2. An apparatus as claimed in claim 1,wherein the rotor is in the formof a solid cylinder and each recording support is guided externally overthe surface of the rotor, the stationary annular nozzle system beingarranged over the external surface of the rotor.

3. An apparatus as claimed in claim 1, wherein the rotor is in the formof a hollow cylinder each recording support is guided over the innersurface of the hollow cylinder, the stationary annular nozzle systembeing arranged inside the hollow. cylinder.

4. An apparatus as claimed in claim 3, wherein each recording support isguided helically over the rotor sur face from the supply roll to thetake-up roll.

5. An apparatus as claimed in claim 4, wherein guide rollers arearranged on the rotor in the vicinity of the supply and take-up rollsfor guiding each recording support supply roll onto the rotor surfaceandfrom the rotor surface onto the take-up roll.

6. An apparatus as claimed in claim 5, wherein the or each supply rolland take-up roll are arranged inside the rotor, and their axes areinclined towards the rotor axis by an amount dependent on the directionin which each sheet recording support runs onto and off from the rotorsurface.

7. An apparatus as claimed in claim 5, wherein each supply roll andtake-up roll is arranged on the rotor axis and the axes of the guiderollers are inclined in relation to the rotor axis in such a way thatthe recording support is turned through into a plane tangential to therotor surface.

'8. An apparatus as claimed in claim 7, wherein the angle of inclinationa of the guide rollers relative to the axis of the rotor is selected inaccordance with the relation a y-U where 'y is the angle at which the oreach recording support runs onto and off from the rotor surface and U isthe looping angle around the guide roller.

9. An apparatus as claimed in claim 8, wherein additional guide rollersare arranged in the vicinity of each supply roll and take-up roll tokeep the looping angle U around the guide rollers constant.

10. An apparatus as claimed in claim 5 wherein at least one of the guiderollers is driven and determines the recording support advance.

11. An apparatus as claimed in claim 5, wherein the ratio of theperipheral speed of the rotor to the rate of recording support sheetadvance is constant.

12. An apparatus as claimed in claim 5, wherein a plurality of supplyrolls are arranged at one end and a corresponding plurality take-uprolls at the other end of the rotor adjacent one another on the rotoraxis.

13. An apparatus as claimed in any claim 12, wherein the axes of theguide rollers extend obliquely of the rotor axis and each recordingsupport is turned through 90 into a plane tangential to the rotorsurface.

14. An apparatus as claimed in claim 13, wherein additional guiderollers which keep the looping angle around the guide rollers constantare arranged in the vicinity of the supply rolls and take-up rolls.

15. An apparatus as claimed in claim 5, wherein the rotor surface ishydrophobic.

16. An apparatus as claimed in claim 3,'wherein each recording supportis guided over the rotor surface parallel to the rotor axis from thesupply roll to the take-up roll.

17. An apparatus as claimed in claim 16, wherein there are a pluralityof supply rolls and take-up rolls which are arranged at the ends of therotor and distributed uniformly over its periphery and perpendicularlyof the rotor axis in such a way that the supply rolls and take-up rollsare opposite one another.

18. An apparatus as claimed in claim 17, wherein contact rollers areprovided on the rotor surface so that the recording supports are inclose contact with the rotor surface in the vicinity of the nozzlesystem.

19. An apparatus as claimed in claim 18, wherein the rotor surface isbevelled frusto-conically towards its ends so that each flat recordingsupport is gradually converted into an arcuate form.

20. An apparatus as claimed in claim 17, wherein the rotor surface isprovided with bores and means for generating a-vacuum inside the rotorso that the sheet recording supports are drawn onto the rotor surface.

1. An apparatus for continuously recording ink-jet pictures comprising arotor having a cylindrical surface, and an annular ink-jet nozzlesystem, wherein the ink-jet nozzle system is stationary in relation tothe rotor, and at least one supply roll and one take-up roll arearranged on the rotor for at least one recording support in guided sheetform each of which is guided over the rotor surface being connected toand rotating with the rotor so that each recording supportsimultaneously makes a rotary and translatory movement in relation tothe stationary nozzle system.
 2. An apparatus as claimed in claim 1,wherein the rotor is in the form of a solid cylinder and each recordingsupport is guided externally over the surface of the rotor, thestationary annular nozzle system being arranged over the externalsurface of the rotor.
 3. An apparatus as claimed in claim 1, wherein therotor is in the form of a hollow cylinder each recording support isguided over the inner surface of the hollow cylinder, the stationaryannular nozzle system being arranged inside the hollow cylinder.
 4. Anapparatus as claimed in claim 3, wherein each recording support isguided helically over the rotor surface from the supply roll to thetake-up roll.
 5. An apparatus as claimed in claim 4, wherein guiderollers are arranged on the rotor in the vicinity of the supply andtake-up rolls for guiding each recording support supply roll onto therotor surface and from the rotor surface onto the take-up roll.
 6. Anapparatus as claimed in claim 5, wherein the or each supply roll andtake-up roll are arranged inside the rotor, and their axes are inclinedtowards the rotor axis by an amount dependent on the direction in whicheach sheet recording support runs onto and off from the rotor surface.7. An apparatus as claimed in claim 5, wherein each supply roll andtake-up roll is arranged on the rotor axis and the axes of the guiderollers are inclined in relation to the rotor axis in such a way thatthe recording support is turned through 90* into a plane tangential tothe rotor surface.
 8. An apparatus as claimed in claim 7, wherein theangle of inclination Alpha of the guide rollers relative to the axis ofthe rotor is selected in accordAnce with the relation Alpha gamma .Uwhere gamma is the angle at which the or each recording support runsonto and off from the rotor surface and U is the looping angle aroundthe guide roller.
 9. An apparatus as claimed in claim 8, whereinadditional guide rollers are arranged in the vicinity of each supplyroll and take-up roll to keep the looping angle U around the guiderollers constant.
 10. An apparatus as claimed in claim 5 wherein atleast one of the guide rollers is driven and determines the recordingsupport advance.
 11. An apparatus as claimed in claim 5, wherein theratio of the peripheral speed of the rotor to the rate of recordingsupport sheet advance is constant.
 12. An apparatus as claimed in claim5, wherein a plurality of supply rolls are arranged at one end and acorresponding plurality take-up rolls at the other end of the rotoradjacent one another on the rotor axis.
 13. An apparatus as claimed inany claim 12, wherein the axes of the guide rollers extend obliquely ofthe rotor axis and each recording support is turned through 90* into aplane tangential to the rotor surface.
 14. An apparatus as claimed inclaim 13, wherein additional guide rollers which keep the looping anglearound the guide rollers constant are arranged in the vicinity of thesupply rolls and take-up rolls.
 15. An apparatus as claimed in claim 5,wherein the rotor surface is hydrophobic.
 16. An apparatus as claimed inclaim 3, wherein each recording support is guided over the rotor surfaceparallel to the rotor axis from the supply roll to the take-up roll. 17.An apparatus as claimed in claim 16, wherein there are a plurality ofsupply rolls and take-up rolls which are arranged at the ends of therotor and distributed uniformly over its periphery and perpendicularlyof the rotor axis in such a way that the supply rolls and take-up rollsare opposite one another.
 18. An apparatus as claimed in claim 17,wherein contact rollers are provided on the rotor surface so that therecording supports are in close contact with the rotor surface in thevicinity of the nozzle system.
 19. An apparatus as claimed in claim 18,wherein the rotor surface is bevelled frusto-conically towards its endsso that each flat recording support is gradually converted into anarcuate form.
 20. An apparatus as claimed in claim 17, wherein the rotorsurface is provided with bores and means for generating a vacuum insidethe rotor so that the sheet recording supports are drawn onto the rotorsurface.